Method of producing a cooking vessel comprising an interior surface of partially coated stainless steel

ABSTRACT

Provided is a method of producing a cooking vessel, including the following steps:forming a blank from a sheet of stainless steel; drawing of the blank to form a cap comprising an interior surface and an exterior surface, the interior surface comprising a flat base area surrounded by a side wall; hot stamping of a diffuser base onto the exterior surface of the cap; engraving of a grid pattern over at least one portion of the base area of the interior surface of the cap to form a network of ribs having top surfaces that extend above the valleys and side surfaces that are distinct from the bottom surfaces of the valleys, said side surfaces of the ribs connecting the top surfaces of the ribs to the bottom surfaces of the valleys, the side surfaces of the ribs forming ramps connecting the top surfaces of the ribs to the bottom surfaces of the valley; sanding of at least the engraved base area of the interior surface of the cap, to create roughness; applying a non-stick coating on at least the sanded, engraved base area; and brushing and/or polishing of at least the sanded, engraved and coated base area to reveal the stainless steel on the top surfaces of the ribs.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of co-pending U.S. patent applicationSer. No. 15/513,705 filed Mar. 23, 2017, which is the United Statesnational phase of International Application No. PCT/FR2015/052541 filedSep. 22, 2015, and claims priority to French Patent Application No.1458977 filed Sep. 23, 2014, the disclosures of which are herebyincorporated in their entirety by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention pertains to the technical field of cooking vesselscomprising an interior surface made of partially coated stainless steel.

More precisely, the present invention pertains to cooking vessels drawnfrom a sheet of stainless steel or from a multilayer sheet having atleast one outer layer of stainless steel, as well as their method ofproduction.

The present invention pertains, in particular, to culinary itemsdesigned to be used on cooktops, such as frying pans or sauce pans, forexample.

The present invention also pertains to the vessels of electronicculinary devices, particularly, but not exclusively, removable vessels.

Description of Related Art

Patent document KR100804387B1 discloses a cooking vessel comprising aninterior surface made of partially coated stainless steel. The interiorsurface has a plurality of valleys, the bases of which bear a non-stickcoating. The interior surface has ribs that are spaced between thevalleys. The uncoated top surfaces of the ribs extend beyond thenon-stick coating covering the bottom surface of the valleys. However,the ribs have uncoated lateral surfaces that extend above the bottomsurface of the valleys. The lateral surfaces of the ribs areperpendicular to the bottom surface of the valleys. The realization ofsuch an object made of stainless steel would be difficult following thedrawing process proposed in this document.

SUMMARY OF THE INVENTION

One objective of the present invention is to propose a cooking vesselwith a cooking surface that offers both ease of cleaning and durability,even when used with utensils made of hard materials, such as metalutensils, for example.

Another objective of the present invention is to propose a method ofproducing a cooking vessel having a cooking surface that offers bothease of cleaning and durability, even when used with utensils made ofhard materials, such as metal utensils, for example.

These objectives are achieved with a cooking vessel comprising a vesselbody having a texturized interior surface made of partially coatedstainless steel, the texturized interior surface having a plurality ofribs that extend above valleys, the valleys having bottom surfacescoated with a non-stick coating, the valleys having top surfaces thatare uncoated and side surfaces distinct from the bottom surfaces of thevalleys, the side surfaces of the ribs connecting the top surfaces ofthe ribs to the bottom surfaces of the valleys, the top surfaces of theribs extending above the non-stick coating that covers the bottomsurfaces of the valleys, such that the non-stick coating extends up theside surfaces of the ribs from the bottom surfaces of the valleys towardthe top surfaces of the ribs, without exceeding the height of the topsurfaces, and that the bottom surfaces of the valleys and the sidesurfaces of the ribs have a roughened surface underneath the non-stickcoating, to promote adhesion of the non-stick coating. Thesearrangements simplify the production of the metal body component of thevessel. These arrangements also improve the adhesion of the non-stickcoating, as the non-stick coating is applied to the entire surface ofthe texturized interior surface, followed by a brushing of the topsurfaces of the ribs. The initial application of a single layer ofnon-stick coating improves the quality of the coating. The durability ofthe cooking vessel is improved, all while preserving the good mechanicalresistance of the cooking surface due to the metal top surfaces of theribs that extend above the coated bottom surfaces of the valleys.

Advantageously, the side surfaces of the ribs form ramps that connectthe top surfaces of the ribs to the bottom surfaces of the valleys. Thisarrangement improves the adhesion of the coating on the side surfaces ofthe ribs.

Also advantageously, the thickness of the non-stick coating is greateron the lower portion of the sides of the ribs than on the upper portionof the sides of the ribs. This arrangement improves the adhesion of thecoating on the lower portion of the side surfaces of the ribs and on theadjacent portions of the bottom surfaces of the valleys.

Also advantageously, the width of the top surfaces of the ribs is lessthan the distance between the top surfaces of two adjacent ribs. Thisarrangement makes it possible to produce a texturized interior surfacewith a coated surface area that is larger than the uncoated metalsurface area of the top surfaces of the ribs.

Also advantageously, the width of the top surfaces of the ribs is lessthan the width of the bottom surfaces of the valleys extending betweenthe two adjacent ribs. This arrangement makes it possible to produce atexturized interior surface with a larger coated surface area.

Also advantageously, the side surfaces of the ribs extend upwards fromthe bottom surfaces of the valleys at an angle (α) less than 45°, andpreferably, at an angle (α) between 20° and 40°. This arrangementsimplifies the realization of the ribs. This arrangement also makes itpossible to improve the adhesion of the coating to the sides of theribs.

Also advantageously, the top surfaces of the ribs are flat. Thisarrangement facilitates the movement of cooking utensils across theribs, to stir, separate or serve foods. This arrangement also simplifiesthe realization of the top surfaces of the ribs. If desired, the topsurfaces of the ribs may be polished, which would reduce the adhesion offoods.

Also advantageously, the ribs are of a trapezoidal configuration. Thisarrangement simplifies the realization of the ribs.

Also advantageously, the depth of cut defined between the top surfacesof the ribs and the bottom surfaces of the valleys is between 0.05 mmand 0.2 mm. This arrangement makes it possible to produce a cookingvessel with the proper features for use, while remaining easy toproduce.

In one embodiment, the non-stick coating has an outer layer ofpolytetrafluoroethylene (PTFE).

In another embodiment, the non-stick coating has an outer layer ofceramic sol-gel.

The vessel body may be made of stainless steel. Thus, advantageously, analuminum heat diffuser plate partially covers the exterior surface ofthe cooking vessel to ensure proper heat distribution. Alsoadvantageously, a stainless steel base plate covers the heat diffuserplate. Thus, advantageously, the base plate is made of ferriticstainless steel, to enable the induction heating of the cooking vessel.

The vessel body may also be made of a multilayer material comprising atleast one outer layer of stainless steel.

Also advantageously, the cooking vessel comprises at least one handlemounted to the vessel body.

Also advantageously, the ribs are interconnected and delimit distinctvalleys. This arrangement facilitates the movement of cooking utensilsacross the ribs, to stir, separate or serve foods.

These objectives may also be achieved with a method to produce a cookingvessel comprising the following steps:

-   -   Realization or provision of a blank from a sheet of stainless        steel,    -   Drawing of the blank to form a cap comprising an interior        surface and an exterior surface, the interior surface comprising        a flat base area surrounded by a side wall,    -   Hot stamping of a diffuser base on the exterior surface of the        cap, with the engraving of a grid pattern, engraving on at least        one portion of the base area of the interior surface of the cap        to form a network of ribs having top surfaces that extend above        the valleys and side surfaces distinct from the bottom surfaces        of the valleys, the side surfaces of the ribs connecting the top        surfaces of the ribs to the bottom surfaces of the valleys,    -   Sanding of at least the engraved base area of the interior        surface of the cap, to create roughness,    -   Application of a non-stick coating on to at least the sanded,        engraved base area,    -   Brushing and/or polishing of at least the coated, sanded,        engraved base area to reveal the stainless steel on the top        surfaces of the ribs.

Thus, advantageously, the method consists of hot stamping base plate offerritic stainless steel onto the surface of the diffuser base oppositethe cap, while the diffuser base is hot stamped onto the exteriorsurface of the cap, to enable the induction heating of the cookingvessel.

These objectives may also be achieved with a method to produce a cookingvessel comprising the following steps:

-   -   Realization or provision of a blank from a multilayer sheet of        steel comprising at least one outer surface made of stainless        steel,    -   Engraving of a grid pattern on at least one portion of said        outer surface made of stainless steel, to form a network of ribs        having top surfaces that extend above the valleys and side        surfaces that are distinct from the bottom surfaces of the        valleys, the side surfaces of the ribs connecting the top        surfaces of the ribs to the bottom surfaces of the valleys,    -   Drawing of the blank to form a cap comprising an interior        surface and an exterior surface, the interior surface comprising        a base area surrounded by a side wall, the ribs extending across        at least one portion of the base area,    -   Sanding of at least the engraved base area to create roughness,    -   Application of a non-stick coating on to at least the sanded,        engraved base area,    -   Brushing and/or polishing of the coated, sanded, engraved base        area to reveal the stainless steel on the top surfaces of the        ribs.

The engraving of a grid pattern may in particular be achieved withstamping, preferably by hot stamping, or by laser engraving.

These objectives may also be achieved with a method to produce a cookingvessel comprising the following steps:

-   -   Realization or provision of a blank from a multilayer sheet of        steel comprising at least one outer surface made of stainless        steel,    -   Drawing of the blank to form a cap comprising an interior        surface formed by said outer surface of stainless steel and an        exterior surface, the interior surface comprising a base area        surrounded by a side wall,    -   Engraving of a grid pattern on at least one portion of the base        area, to form a network of ribs having top surfaces that extend        above the valleys and side surfaces distinct from the bottom        surfaces of the valleys, the side surfaces of the ribs        connecting the top surfaces of the ribs to the bottom surfaces        of the valleys,    -   Sanding of at least the engraved base area to create roughness,    -   Application of a non-stick coating on to at least the sanded,        engraved base area,    -   Brushing and/or polishing of the coated, sanded, engraved base        area to reveal the stainless steel on the top surfaces of the        ribs.

The engraving of a grid pattern may in particular be achieved withstamping, preferably by hot stamping, or by laser engraving.

Thus, advantageously, a polishing of the top surfaces of the ribs isperformed prior to the application of the non-stick coating, to limitthe adhesion of the non-stick coating on the top surfaces of the ribs.

These objectives may also be achieved with a cooking vessel obtained bya method according to the aforementioned characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more clearly understood upon review of one exampleof one embodiment of a cooking vessel and of three embodiments of amethod to produce a cooking vessel, provided as non-limiting examples,illustrated in the annexed figures, in which:

FIG. 1 is a schematic top view of one embodiment of a cooking vesselaccording to the invention, with FIG. 1a representing an enlargedsectional view of the interior surface of the cooking vessel representedin FIG. 1;

FIG. 2 is a partial enlarged cross-sectional view of the cooking vesselillustrated in FIGS. 1 and 1 a, taken along section line II-II of FIG. 1a;

FIGS. 3 to 8 schematically illustrate the steps of one initialembodiment of a method to produce a cooking vessel according to theinvention;

FIG. 3 is a schematic cross-section view of a stainless steel blank;

FIG. 4 is a schematic cross-section view of the blank represented inFIG. 3, after drawing;

FIG. 5 is a schematic cross-section view of the drawn blank representedin FIG. 4, after assembly with a diffuser base on the outer surface ofthe base of the blank and engraving of the base of the inner surface ofthe blank, with FIG. 5a representing an enlarged sectional view of thetop portion of the base of the inner surface of the blank represented inFIG. 5;

FIG. 6 is a schematic cross-section of the drawn blank represented inFIG. 5, after sanding of the base of the inner surface of the blank,with FIG. 6a representing an enlarged sectional view of the upperportion of the base of the inner surface of the blank represented inFIG. 6;

FIG. 7 is a schematic cross-section of the drawn, sanded blankrepresented in FIG. 6, after the application of a coating on the base ofthe inner surface of the blank, with FIG. 7a representing an enlargedsectional view of the upper portion of the base of the inner surface ofthe blank represented in FIG. 7;

FIG. 8 is a schematic cross-section of the drawn, sanded, coated blankrepresented in FIG. 7, after the brushing and/or polishing of the topsurfaces of the ribs formed on the base of the inner surface of theblank, with FIG. 8a representing an enlarged sectional view of the upperportion of the base of the inner surface of the blank represented inFIG. 8;

FIGS. 9 to 14 schematically depict the steps of a second embodiment of amethod to produce a cooking vessel according to the invention;

FIG. 9 is a schematic cross-section of a three-layer blank comprising atleast one outer surface of stainless steel, the three layers beingdepicted in FIG. 9a , showing one portion of the blank represented inFIG. 9;

FIG. 10 is a schematic cross-section view of the blank represented inFIG. 9, after the engraving of one portion of the inner surface of theblank, with FIG. 10a representing an enlarged sectional view of theupper portion of the inner surface of the blank represented in FIG. 10;

FIG. 11 is a schematic cross-section view of the engraved blankrepresented in FIG. 10, after drawing;

FIG. 12 is a schematic cross-section of the engraved, drawn blankrepresented in FIG. 11, after the sanding of the base of the innersurface of the blank, with FIG. 12a representing an enlarged sectionalview of the upper portion of the base of the inner surface of the blankrepresented in FIG. 12;

FIG. 13 is a schematic cross-section of the engraved, drawn, sandedblank represented in FIG. 12 after the application of a coating on thebase of the inner surface of the blank, with FIG. 13a representing anenlarged sectional view of the upper portion of the base of the innersurface of the blank represented in FIG. 13;

FIG. 14 is a schematic cross-section of the drawn, sanded, coated blankrepresented in FIG. 13, after the brushing and/or polishing of the topsurfaces of the ribs formed on the base of the inner surface of theblank, with FIG. 14a representing an enlarged sectional view of theupper portion of the base of the inner surface of the blank representedin FIG. 14;

FIGS. 15 to 20 schematically depict the steps of a third embodiment of amethod to produce a cooking vessel according to the invention;

FIG. 15 is a schematic cross-section of a three-layer blank comprisingat least one outer surface of stainless steel, the three layers beingdepicted in FIG. 15a , showing one portion of the blank represented inFIG. 15;

FIG. 16 is a schematic cross-section view of the blank represented inFIG. 15, after drawing;

FIG. 17 is a schematic cross-section of the drawn blank represented inFIG. 16, after the engraving of one portion of the inner surface of theblank, with FIG. 17a representing an enlarged sectional view of theupper portion of the inner surface of the blank represented in FIG. 17;

FIG. 18 is a schematic cross-section of the engraved, drawn blankrepresented in FIG. 17, after the sanding of the base of the innersurface of the blank, with FIG. 18a representing an enlarged sectionalview of the upper portion of the base of the inner surface of the blankrepresented in FIG. 18;

FIG. 19 is a schematic cross-section of the engraved, drawn, sandedblank represented in FIG. 19 after the application of a coating on thebase of the inner surface of the blank, with FIG. 19a representing anenlarged sectional view of the upper portion of the base of the innersurface of the blank represented in FIG. 19; and

FIG. 20 is a schematic cross-section of the drawn, sanded, coated blankrepresented in FIG. 19, after the brushing and/or polishing of the topsurfaces of the ribs formed on the base of the inner surface of theblank, with FIG. 20a representing an enlarged sectional view of theupper portion of the base of the inner surface of the blank representedin FIG. 20.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates one example embodiment of a cooking vessel (1)comprising a vessel body (2) having a texturized interior surface (3)made of partially-coated stainless steel. The texturized interiorsurface (3) forms a cooking surface. As represented in FIG. 1, thetexturized interior surface (3) is surrounded by a non-texturizedinterior surface (4). The non-texturized interior surface (4) may becoated or uncoated. The coated, non-texturized interior surface (4)would preferably have the same coating as the texturized interiorsurface (3). The coated, non-texturized interior surface is preferablymade of polished stainless steel.

In one embodiment illustrated in FIG. 1, the texturized interior surface(3) extends over a flat portion forming the base of the vessel body (2),and the non-texturized interior surface (4) extends over a side wallextending up from the base of the vessel body (2). The cooking vessel(1) may be, in particular, a frying pan or saucepan, or even a vesselfrom an electronic culinary device with a flat base.

In one variation, the texturized interior surface (3) may extend atleast partially up the side wall from the base of the vessel body (2).The vessel body (2) thus does not necessarily present a non-texturizedinterior surface (4). The texturized interior surface (3) may thus coverthe entirety of the interior of the cooking vessel.

In one variation, the base of the vessel body (2) is not necessarilyflat. The cooking vessel (1) may thus, in particular, be a wok, or maybe a vessel from an electronic culinary device with a concave base.

As illustrated in FIG. 1, the cooking vessel (1) comprises a handle (5)mounted to the vessel body (2). As desired, the cooking vessel (1) maycomprise at least one other handle mounted to the vessel body (2). Thevessel body (2) depicted in FIG. 1 has a circular form. In onevariation, the vessel body (2) may have other forms, in particular anoval or elliptical form.

In one initial embodiment, the vessel body (2) may be produced from ablank (20) of stainless steel, depicted in FIG. 3. Preferably, thestainless steel is of the austenitic variety and in particular astainless steel of the grade 304, or a ferritic variety, and inparticular a stainless steel of the grade 441. To ensure good heatdistribution across the interior surface of the vessel body (2) thevessel body (2) advantageously has a corresponding diffuser base (8)made of a highly heat-conductive material (aluminum alloy, copper,etc.), depicted in FIG. 5. As desired, the corresponding diffuser base(8) may be positioned between the vessel body (2) and a base plate (9)preferably made of ferritic stainless steel, to enable the inductionheating of the cooking vessel (1).

In a second embodiment, the vessel body (2) may be produced from amultilayer blank (30; 40) comprising at least one outer surface (30 a;40 a) made of stainless steel, depicted in FIGS. 9 and 15. The outersurface (30 a; 40 a) made of stainless steel is intended to form theinterior surface of the vessel body (2). The outer surface (30 a; 40 a)made of stainless steel is, preferably, made of austenitic stainlesssteel, for example, a stainless steel of the grade 304. The blank (30;40) comprises a core (30 b; 40 b) made of a material that is highlyheat-conductive or formed by an assembly of materials that are highlyheat-conductive (aluminum alloy, copper, etc.). The blank preferablycomprises another outer surface (30 c; 40 c) made of ferritic stainlesssteel, to enable the induction heating of the cooking vessel (1).

As is more clearly depicted in FIG. 1a , the texturized interior surface(3) of the vessel body (2) has a plurality of ribs (10). The ribs (10)form a screen on the texturized interior surface (3).

As is more clearly depicted in FIG. 2, the ribs (10) extend above thevalleys (15). The valleys (15) have bottom surfaces (16) that are coatedwith a non-stick coating (7). The ribs (10) have uncoated top surfaces(11). The ribs (10) have side surfaces (12) that are distinct from thebottom surfaces (16) of the valleys (15). In other words, the sidesurfaces (12) of the ribs (10) extend above the bottom surfaces (16) ofthe valleys (15). The side surfaces (11)(12) of the ribs (10) extendabove the non-stick coating (7) covering the bottom surfaces (16) of thevalleys (15). The side surfaces (12) of the ribs (10) connect the topsurfaces (11) of the ribs (10) to the bottom surfaces (16) of thevalleys (15). The non-stick coating (7) extends up the side surfaces(12) of the ribs (10) from the bottom surfaces (16) of the valleys (15)toward the top surfaces (11) of the ribs (10), without exceeding theheight of the top surfaces (11). Thus the top uncoated surfaces (11)form a support surface for a cooking utensil used to stir, separate orserve foods, such as, for example, a spatula.

The non-stick coating (7) covering the valleys (15) is protected fromthe movements of the spatula by the top surfaces (11) of the ribs (10).The ribs (10) are preferably distributed across the texturized interiorsurface (3) of the vessel body (2) such that the distance between thetop surfaces (11) of two neighboring, or adjacent, ribs (10) is lessthan or equal to 2 cm, irrespective of orientation.

The narrowness of the top surfaces (11) of the ribs (10) makes itpossible to minimize contact between foods and the surfaces made ofstainless steel, and thus to improve the ease of cleaning of the cookingsurface. The width of the top surfaces (11) as defined by their smallestsurface dimension is advantageously between 100 μm and 2 mm.

As illustrated in FIGS. 1 and 1 a, the texturized interior surface (3)comprises a stainless steel grid. The grid is formed by the top surfaces(11) of the ribs (10) depicted in FIG. 2. The ribs (10) areinterconnected and delimit distinct valleys (15). In other words, theribs (10) separate the valleys (15). The ribs (10) thus form acontinuous grid network. The crevices in the grid are filled by thenon-stick coating (7).

More specifically in the embodiment illustrated in FIGS. 1 and 1 a, theribs (10) extend in two perpendicular directions and form a square grid.

The stainless steel grid formed by the top surfaces (11) of the ribs(10) ensures the protection of the non-stick coating (7). The stainlesssteel grid may take the form of a polygon grid (for example a square,rectangular, triangular, diamond or hexagonal grid), or an elliptic grid(for example, juxtaposed ellipses or circles). The surface of the gridnetwork (irrespective of form) is preferably between 0.25 mm² and 1 cm²,The ratio between the surface defined by the grid and the total surface(of the area in which the grid is present) is between 0.02 and 0.25 Inother words, the top surfaces (11) of the ribs (10) constitute between2% to 25% of the cooking surface.

In one variation, two adjacent ribs (10) are not necessarily parallel orperpendicular.

In one variation, the grid is not necessarily continuous. At least somevalleys (15) may be interconnected. At least some ribs (10) may besurrounded by valleys (15).

As depicted in FIG. 2, the bottom surfaces (16) of the valleys (15) andthe side surfaces (12) of the ribs (10) have a roughened surface (6)underneath the non-stick coating (7) to improve the adhesion of thenon-stick coating (7).

In the embodiment depicted in the figures, the width of the top surfaces(11) of the ribs (10) is less than the width of the bottom surfaces (16)of the valleys (15) extending between two adjacent ribs (10). The topsurfaces (11) of the ribs (10) are flat. The ribs (10) are of atrapezoidal configuration.

As depicted in FIG. 2, the side surfaces (12) of the ribs (10) formramps that connect the top surfaces (11) of the ribs (10) to the bottomsurfaces (16) of the valleys (15). In other words, the side surfaces(12) of the ribs (10) are inclined and form slopes extending up from thebottom surfaces (16) of the valleys (15). Thus the non-stick coating (7)covering the bottom surfaces (16) of the valleys (15) may extend upprogressively to cover the side surfaces (12) of the ribs (10). Asdepicted in FIG. 2, the thickness of the non-stick coating is greater onthe lower portion of the side surfaces (12) of the ribs (10) than on theupper portion of the side surfaces (12) of the ribs (10).

Advantageously, as depicted in FIG. 2, the side surfaces (12) of theribs (10) extend up from the bottom surfaces (16) of the valleys (15) atan angle (α) less than 45°. Preferably, the angle is between 20° and40°.

The depth of cut defined between the top surfaces (11) of the ribs (10)and the bottom surfaces (16) of the valleys (15) is preferably between0.05 mm and 0.2 mm. The intended depth of cut is, for example,approximately 0.1 mm.

As depicted in FIG. 2, the side surfaces (12) of the ribs (10) arecovered by the non-stick coating (7); the top surfaces (11) of the ribs(10) are not covered by the non-stick coating (7).

The non-stick coating (7) may be selected from various types.

In one embodiment, the non-stick coating (7) has an outer layer of PTFE(polytetrafluoroethylene).

In another embodiment, the non-stick coating (7) has an outer layer ofceramic sol-gel.

As desired, at least one intermediary layer may be applied underneaththe outer layer.

The non-stick coating (7), as it constitutes a significant proportion,typically the majority, of the cooking surface, makes it possible toobtain an ease of cleaning. The presence of the top surfaces (11) of theribs (10) makes it possible to produce a support surface allowing forthe use of rigid utensils used to stir, cut and serve foods, and inparticular the use of metal utensils such as spatulas or knives, withoutdamaging the non-stick coating (7) on the bottom surfaces (16) of thevalleys (15).

This construction of the cooking surface makes it possible to combinethe ease of cleaning guaranteed by the non-stick coating (7) with theimproved durability of the cooking vessel (1) guaranteed by the metalgrid formed by the top surfaces (11) of the ribs (10) that protect theintegrity of the non-stick coating (7) on the bottom surfaces (16) ofthe valleys (15) against mechanical stress.

The juxtaposition of the uncoated top surfaces (11) and the coatedvalleys (15) improves scratch-resistance without sacrificing non-stickproperties. This juxtaposition also makes it possible to differentiatethe cooking surface.

When a stainless steel sheet is used, the method to produce a cookingvessel (1) according to the invention may comprise the following steps,depicted in FIGS. 3 to 8 a:

-   -   Realization or provision of a blank (20) from a sheet of        stainless steel,    -   Drawing of the blank (20) to form a cap (21) comprising an        interior surface (22) and an exterior surface (23), the interior        surface (22) comprising a flat base area (24) surrounded by a        side wall (25),    -   Hot stamping of a diffuser base (8) onto the exterior surface        (23) of the cap (21), with the engraving of a grid pattern (27)        on at least one portion of the base area (24) of the interior        surface (22) of the cap (21), to form a network of ribs (10)        having top surfaces (11) that extend above the valleys (15) and        side surfaces (12) that are distinct from the bottom surfaces        (16) of the valleys (15) the side surfaces (12) of the ribs (10)        connecting the top surfaces (11) of the ribs (10) to the bottom        surfaces (16) of the valleys (15), Sanding of at least the        engraved base area (24) of the interior surface (22) of the cap        (21) to create roughness (26),    -   Application of a non-stick coating (7) onto at least the        engraved, sanded base area (24),    -   Brushing and/or polishing of at least the engraved, sanded,        coated base area (24) to reveal the stainless steel on the top        surfaces (11) of the ribs (10).

Grid patterning of the base area (24) of the cooking surface is thusperformed during the hot stamping process. A punch is used that bearsthe grid pattern (or design) intended to be engraved on the base of thecooking surface. The grid pattern may, for example, be engraved on thepunch using electro-spark engraving.

The use of appropriate parameters during the stamping (preheatingtemperature, stamping power, etc.) thus makes it possible to ensure theadhesion of the stamped diffuser base (8) and to engrave the gridpattern on the base area (24) of the interior surface (22) with auniform depth, the targeted depth being approximately 0.1 mm. Thestamping operation makes it possible to engrave the design on the flatportion of the cooking vessel (1). This process thus does not allow forany engraving of the surface at the bending radius between the base area(24) and the side wall (25), or of the side wall (25).

In a preferred embodiment, the process consists of hot stamping a baseplate (9) of ferritic stainless steel onto the surface of the diffuserbase (8) that is opposite the cap (21), when the diffuser base (8) ishot stamped onto the exterior surface (23) of the cap (21). A cookingvessel (1) that may be heated by induction may thus be obtained. Thebase plate (9) preferably has the form of a disc. As desired, the baseplate (9) may be added.

When a multilayer stainless steel sheet comprising at least one outersurface made of stainless steel is used, the method to produce a cookingvessel (1) according to the invention may comprise the following steps,depicted in FIGS. 9 to 14 a:

-   -   Realization or provision of a blank (30) from a multilayer sheet        of steel (30 a; 30 b; 30 c) comprising at least one outer        surface (30 a) made of stainless steel,    -   Engraving of a grid pattern (37) of at least one portion of said        outer surface (30 a) of stainless steel to form a network of        ribs (10) having top surfaces (11) that extend above the valleys        (15) and side surfaces (12) that are distinct from the bottom        surfaces (16) of the valleys (15), the side surfaces (12) of the        ribs (10) connecting the top surfaces (11) of the ribs (10) to        the bottom surfaces (16) of the valleys (15),    -   Drawing of the blank (30) to form a cap (31) comprising an        interior surface (32) and an exterior surface (33), the interior        surface (32) comprising a base area (34) surrounded by a side        wall (35), the ribs (10) extending across at least a portion of        the base area (34),    -   Sanding of at least the engraved base area (34) to create        roughness (36),    -   Application of a non-stick coating (7) onto at least the        engraved, sanded base area (34),    -   Brushing and/or polishing of the engraved, sanded, coated base        area (34) to reveal the stainless steel on the top surfaces (11)        of the ribs (10).

The design may be engraved in a uniform manner across the entire cookingsurface formed by the interior surface (32) as drawing does not degradethe grid pattern (37).

A stamping operation, preferably hot stamping, may be used to engravethe design. This operation makes it possible to engrave the desired gridpattern on the outer surface (30 a) made of stainless steel. In the samemanner described for a cooking vessel with a stamped base, a punch andelectro-spark engraved screen may be used for the stamping operation.

In the aforementioned embodiment, the stamping operation is performedprior to drawing.

In one variation, the drawing of the blank may be performed prior to theengraving of a grid pattern. The method to produce a cooking vessel (1)according to the invention may thus comprise the following steps,depicted in FIGS. 15 to 20 a:

-   -   Realization or provision of a blank from a multilayer sheet of        steel (40 a; 40 b; 40 c) comprising at least one outer surface        (40 a) made of stainless steel,    -   Drawing of the blank (40) to form a cap (41) comprising an        interior surface (42) formed by said outer surface (40 a) made        of stainless steel and an exterior surface (43), the interior        surface (42) comprising a flat base area (44) surrounded by a        side wall (45),    -   Engraving of a grid pattern (47) over at least one portion of        the base area (44) to form a network of ribs (10) having top        surfaces (11) that extend above the valleys (15) and side        surfaces (12) that are distinct from the bottom surfaces (16) of        the valleys (15), the side surfaces (12) of the ribs (10)        connecting the top surfaces (11) of the ribs (10) to the bottom        surfaces (16) of the valleys (15),    -   Sanding of at least the engraved base area (44) to create        roughness (46),    -   Application of a non-stick coating (7) onto at least the        engraved, sanded base area (44),    -   Brushing and/or polishing of the engraved, sanded, coated base        area (44) to reveal the stainless steel on the top surfaces (11)        of the ribs (10).

The engraving of a grid pattern (47) is then performed on at least oneportion of the flat base area (44) after the blank (40) is drawn. Thisprocess thus does not allow for any engraving of the surface at thebending radius between the base area (44) and the side wall (45), or onthe side wall (45).

The surface to be coated is sanded to create sufficient roughness (26;36; 46) to enable the maximum adhesion of the non-stick coating (7)without damaging the top surfaces (11) formed during the engravingprocess.

Optionally, the top surfaces (11) of the ribs (10) are polished prior tothe application of the non-stick coating (7) to limit the adhesion ofthe non-stick coating (7) on the top surfaces (11) of the ribs (10).

For PTFE-type non-stick coatings, sanding may be performed, inparticular, with a brown corundum (α-alumina). The following roughnessparameters are envisioned for roughness (26; 36; 46):

Ra≥2 μm, preferably 3 μm≤Ra≤5 μm

Rz≥25 μm, preferably 30 μm≤Rz≤50 μm

Ra and Rz are defined in the ISO standard 4287. Ra is defined as thearithmetical mean deviation of the assessed profile; Rz represents theaverage distance between the five highest peaks and 5 lowest valleys.

Surface topography may be studied, in particular, with a diamond-tippedstylus probe profilometer, or with an optical profiler such as anAltisurf® device, in which a chromatic confocal sensor enablesnon-contact profilometry. The study of this surface topography makes itpossible to determine the surface roughness parameters, as definedabove.

The PTFE-type non-stick coating (7) may be sprayed onto the surfaceafter the surface has been sanded. As desired, at least one intermediarylayer may be applied prior to applying the outer layer of the PTFE-typenon-stick coating (7). After cooking the non-stick coating (7) at 420°C., the texturized interior surface (3), and, as desired, thenon-texturized interior surface (4) of the interior of the cookingvessel (2) are polished. The polishing makes it possible to reveal thestainless steel grid network by selectively revealing the top surfaces(11) of the ribs (10), the coated valley (15) being unaffected by thisoperation. Furthermore, the exterior of the vessel body (2) is alsopolished to remove the oxide layer that appears during the PTFE coatingcooking process.

When a non-stick coating (7) has an outer layer of ceramic sol-gel, thesurface to be re-coated is sanded to create enough roughness to ensuremaximum adhesion of the non-stick coating (7) without damaging the topsurfaces (11) formed during the engraving process. Sanding may beperformed, in particular, with a zirconia corundum abrasive.

When ceramic coatings are used, the sanding conditions are adjusted toproduce the following roughness parameters for roughness (26; 36; 46):

Ra≥1.5 μm, preferably 2 μm≤Ra≤3 μm

Rz≥10 μm, preferably 15 μm≤Rz≤30 μm

The ceramic sol-gel non-stick coating (7) may be sprayed onto thesurface that has undergone a sanding treatment. A coating thickness of20 to 40 μm may be targeted. The cooking cycle for the sol-gel coatingapplied to a stainless steel substrate may comprise an increase intemperature to 250° C. over a period of 15 minutes, followed by 15minutes of cooking at 250° C. Polishing of the interior of the cookingvessel (2) makes it possible to reveal the surface of the stainlesssteel grid network formed by the top surfaces (11) of the ribs (10), byselectively removing the sol-gel coating from the top surfaces (11) ofthe ribs (10). The ceramic-coated valleys (15) are not affected by suchan operation. Furthermore, the exterior of the vessel body (2) is alsopolished to remove the oxide layer that appears during the sol-gelcooking process.

As depicted in FIGS. 8a, 14a and 20a , the side surfaces (12) of theribs (10) form ramps that connect the top surfaces (11) of the ribs (10)to the bottom surfaces (16) of the valleys (15).

As depicted in FIGS. 8a, 14a and 20a , the side surfaces (12) of theribs (10) are covered by the non-stick coating (7); the top surfaces(11) of the ribs (10) are not covered by the non-stick coating (7).

In one variation, the ribs (10) are not necessarily produced by hot orcold stamping. Laser engraving may be performed on the blank (20; 30;40) before or after drawing. The use of a high-powered laser makes itpossible to obtain both the desired depth of cut (approximately 50 to100 μm) and the desired narrowness of the top surfaces (11) of the ribs(10). As desired, a stamping operation may be used, in particular toassemble the diffuser base (8) and, where applicable, the ferriticstainless steel base plate (9) when the blank (20) is made of stainlesssteel.

The present invention is in no way limited to the described exampleembodiments and variations, but encompasses numerous modificationswithin the scope of the claims.

The invention claimed is:
 1. A method of producing a cooking vessel,comprising: forming a blank from a sheet of stainless steel; drawing ofthe blank to form a cap comprising an interior surface and an exteriorsurface, the interior surface comprising a flat base area surrounded bya side wall; hot stamping of a diffuser base onto the exterior surfaceof the cap, with engraving of a grid pattern over at least one portionof the base area of the interior surface of the cap to form a network ofribs having top surfaces that extend above bottom surfaces of valleysand side surfaces that are distinct from the bottom surfaces of thevalleys, the side surfaces of the ribs connecting the top surfaces ofthe ribs to the bottom surfaces of the valleys, the side surfaces of theribs forming ramps connecting the top surfaces of the ribs to the bottomsurfaces of the valleys, and further hot stamping a base plate offerritic stainless steel, wherein the base plate is in a form of a disc,onto a surface of the diffuser base opposite the cap when the diffuserbase is hot stamped onto the exterior surface of the cap; sanding of atleast the engraved base area of the interior surface of the cap, tocreate roughness; applying a non-stick coating on at least the sanded,engraved base area; brushing and/or polishing of at least the sanded,engraved and coated base area to reveal the stainless steel on the topsurfaces of the ribs; and polishing the top surfaces of the ribs priorto the application of the non-stick coating, to limit adhesion of thenon-stick coating on the top surfaces of the ribs.
 2. The method ofobtaining the cooking vessel according to claim 1, wherein the sidesurfaces of the ribs extend upward from the bottom surfaces of thevalleys at an angle less than 45°.
 3. The method of obtaining thecooking vessel according to claim 1, wherein a thickness of thenon-stick coating is greater on a lower portion of the side surfaces ofthe ribs than on an upper portion of the side surfaces of the ribs.
 4. Amethod of producing a cooking vessel, comprising: forming a blank from amultilayer stainless steel sheet comprising at least one outer surfacemade of stainless steel; engraving of a grid pattern by stamping, hotstamping or laser engraving on at least one portion of the outer surfacemade of stainless steel of the blank, to form a grid of ribs having topsurfaces extending above bottom surfaces of valleys and side surfacesthat are distinct from the bottom surfaces of the valleys, the sidesurfaces connecting the top surfaces of the ribs to the bottom surfacesof the valleys, the side surfaces of the ribs forming ramps connectingthe top surfaces of the ribs to the bottom surfaces of the valleys;drawing the blank to form a cap comprising an interior surface and anexterior surface, the interior surface comprising a base area surroundedby a side wall, the ribs extending over at least one portion of the basearea; sanding of at least the engraved base area to create roughness;applying a non-stick coating on at least the sanded, engraved base area;brushing and/or polishing of the sanded, engraved and coated base area,to reveal the stainless steel on the top surfaces of the ribs; andpolishing the top surfaces of the ribs prior to the application of thenon-stick coating, to limit adhesion of the non-stick coating on the topsurfaces of the ribs.
 5. The method of obtaining the cooking vesselaccording to claim 4, wherein the side surfaces of the ribs extendupward from the bottom surfaces of the valleys at an angle less than45°.
 6. The method of obtaining the cooking vessel according to claim 4,wherein a thickness of the non-stick coating is greater on a lowerportion of the side surfaces of the ribs than on an upper portion of theside surfaces of the ribs.
 7. A method of producing a cooking vessel,comprising: forming a blank from a multilayer stainless steel sheetcomprising at least one outer surface made of stainless steel; stampingof the blank to form a cap comprising an interior surface formed by saidstainless steel outer surface and an exterior surface, the interiorsurface comprising a base area surrounded by a side wall; engraving of agrid pattern by stamping, hot stamping or laser engraving over at leastone portion of the base area, to form a grid of ribs having top surfacesextending above bottom surfaces of valleys and side surfaces that aredistinct from the bottom surfaces of the valleys, the side surfaces ofthe ribs connecting the top surfaces of the ribs to the bottom surfacesof the valleys, the side surfaces of the ribs forming ramps connectingthe top surfaces of the ribs to the bottom surfaces of the valleys;sanding of at least the engraved base area to create roughness; applyinga non-stick coating on at least the sanded, engraved base area; brushingand/or polishing of the sanded, engraved, and coated base area to revealthe stainless steel on the top surfaces of the ribs; and polishing thetop surfaces of the ribs prior to the application of the non-stickcoating, to limit adhesion of the non-stick coating on the top surfacesof the ribs.
 8. The method of obtaining the cooking vessel according toclaim 7, wherein the side surfaces of the ribs extend upward from thebottom surfaces of the valleys at an angle less than 45°.
 9. The methodof obtaining the cooking vessel according to claim 7, wherein athickness of the non-stick coating is greater on a lower portion of theside surfaces of the ribs than on an upper portion of the side surfacesof the ribs.